libpipeline (1.5.7)
1 /* Copyright (C) 1989, 1990, 1991, 1992, 2000, 2002
2 * Free Software Foundation, Inc.
3 * Copyright (C) 2003-2017 Colin Watson.
4 * Written for groff by James Clark (jjc@jclark.com)
5 * Adapted for man-db by Colin Watson.
6 *
7 * This file is part of libpipeline.
8 *
9 * libpipeline is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or (at
12 * your option) any later version.
13 *
14 * libpipeline is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with libpipeline; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
22 * USA.
23 */
24
25 #ifndef PIPELINE_H
26 #define PIPELINE_H
27
28 #ifdef __cplusplus
29 extern "C" {
30 #endif
31
32 #include <stdarg.h>
33 #include <stdio.h>
34 #include <sys/types.h>
35
36 /* GCC version checking borrowed from glibc. */
37 #if defined(__GNUC__) && defined(__GNUC_MINOR__)
38 # define PIPELINE_GNUC_PREREQ(maj, min) \
39 ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
40 #else
41 # define PIPELINE_GNUC_PREREQ(maj, min) 0
42 #endif
43
44 /* Does this compiler support format string checking? */
45 #if PIPELINE_GNUC_PREREQ(2, 0)
46 # define PIPELINE_ATTR_FORMAT_PRINTF(a, b) \
47 __attribute__ ((__format__ (__printf__, a, b)))
48 #else
49 # define PIPELINE_ATTR_FORMAT_PRINTF(a, b)
50 #endif
51
52 /* Does this compiler support marking variables as unused? */
53 /* This is no longer used internally and isn't documented as part of
54 * libpipeline's public API, but is preserved just in case somebody used it
55 * anyway.
56 */
57 #if PIPELINE_GNUC_PREREQ(2, 4)
58 # define PIPELINE_ATTR_UNUSED __attribute__ ((__unused__))
59 #else
60 # define PIPELINE_ATTR_UNUSED
61 #endif
62
63 /* Does this compiler support marking functions as non-returning? */
64 #if PIPELINE_GNUC_PREREQ(2, 5)
65 # define PIPELINE_ATTR_NORETURN __attribute__ ((__noreturn__))
66 #else
67 # define PIPELINE_ATTR_NORETURN
68 #endif
69
70 /* Does this compiler support unused result checking? */
71 #if PIPELINE_GNUC_PREREQ(3, 4)
72 # define PIPELINE_ATTR_WARN_UNUSED_RESULT \
73 __attribute__ ((__warn_unused_result__))
74 #else
75 # define PIPELINE_ATTR_WARN_UNUSED_RESULT
76 #endif
77
78 /* Does this compiler support sentinel checking? */
79 #if PIPELINE_GNUC_PREREQ(4, 0)
80 # define PIPELINE_ATTR_SENTINEL __attribute__ ((__sentinel__))
81 #else
82 # define PIPELINE_ATTR_SENTINEL
83 #endif
84
85 typedef void pipecmd_function_type (void *);
86 typedef void pipecmd_function_free_type (void *);
87
88 struct pipecmd;
89 typedef struct pipecmd pipecmd;
90
91 struct pipeline;
92 typedef struct pipeline pipeline;
93
94 /* ---------------------------------------------------------------------- */
95
96 /* Functions to build individual commands. */
97
98 /* Construct a new command. */
99 pipecmd *pipecmd_new (const char *name);
100
101 /* Convenience constructors wrapping pipecmd_new() and pipecmd_arg().
102 * Terminate arguments with NULL.
103 */
104 pipecmd *pipecmd_new_argv (const char *name, va_list argv);
105 pipecmd *pipecmd_new_args (const char *name, ...) PIPELINE_ATTR_SENTINEL;
106
107 /* Split argstr on whitespace to construct a command and arguments,
108 * honouring shell-style single-quoting, double-quoting, and backslashes,
109 * but not other shell evil like wildcards, semicolons, or backquotes. This
110 * is a backward-compatibility hack to support old configuration file
111 * directives; please try to avoid using it in new code.
112 */
113 pipecmd *pipecmd_new_argstr (const char *argstr);
114
115 /* Construct a new command that calls a given function rather than executing
116 * a process. The data argument is passed as the function's only argument,
117 * and will be freed before returning using free_func (if non-NULL).
118 *
119 * pipecmd_* functions that deal with arguments cannot be used with the
120 * command returned by this function.
121 */
122 pipecmd *pipecmd_new_function (const char *name, pipecmd_function_type *func,
123 pipecmd_function_free_type *free_func,
124 void *data);
125
126 /* Construct a new command that runs a sequence of commands. The commands
127 * will be executed in forked children; if any exits non-zero then it will
128 * terminate the sequence, as with "&&" in shell.
129 *
130 * pipecmd_* functions that deal with arguments cannot be used with the
131 * command returned by this function.
132 */
133 pipecmd *pipecmd_new_sequencev (const char *name, va_list cmdv);
134 pipecmd *pipecmd_new_sequence (const char *name, ...) PIPELINE_ATTR_SENTINEL;
135
136 /* Return a new command that just passes data from its input to its output. */
137 pipecmd *pipecmd_new_passthrough (void);
138
139 /* Return a duplicate of a command. */
140 pipecmd *pipecmd_dup (pipecmd *cmd);
141
142 /* Add an argument to a command. */
143 void pipecmd_arg (pipecmd *cmd, const char *arg);
144
145 /* Convenience function to add an argument with printf substitutions. */
146 void pipecmd_argf (pipecmd *cmd, const char *format, ...)
147 PIPELINE_ATTR_FORMAT_PRINTF (2, 3);
148
149 /* Convenience functions wrapping pipecmd_arg().
150 * Terminate arguments with NULL.
151 */
152 void pipecmd_argv (pipecmd *cmd, va_list argv);
153 void pipecmd_args (pipecmd *cmd, ...) PIPELINE_ATTR_SENTINEL;
154
155 /* Split argstr on whitespace to add a list of arguments, honouring
156 * shell-style single-quoting, double-quoting, and backslashes, but not
157 * other shell evil like wildcards, semicolons, or backquotes. This is a
158 * backward-compatibility hack to support old configuration file directives;
159 * please try to avoid using it in new code.
160 */
161 void pipecmd_argstr (pipecmd *cmd, const char *argstr);
162
163 /* Return the number of arguments to this command. Note that this includes
164 * the command name as the first argument, so the command 'echo foo bar' is
165 * counted as having three arguments.
166 */
167 int pipecmd_get_nargs (pipecmd *cmd);
168
169 /* Set the nice(3) value for this command. Defaults to 0. Errors while
170 * attempting to set the nice value are ignored, aside from emitting a debug
171 * message.
172 */
173 void pipecmd_nice (pipecmd *cmd, int nice);
174
175 /* If discard_err is non-zero, redirect this command's standard error to
176 * /dev/null. Otherwise, and by default, pass it through.
177 */
178 void pipecmd_discard_err (pipecmd *cmd, int discard_err);
179
180 /* Change to this directory while running this command. */
181 void pipecmd_chdir (pipecmd *cmd, const char *directory);
182
183 /* Change to the directory given by this open file descriptor while running
184 * this command. */
185 void pipecmd_fchdir (pipecmd *cmd, int directory_fd);
186
187 /* Set an environment variable while running this command. */
188 void pipecmd_setenv (pipecmd *cmd, const char *name, const char *value);
189
190 /* Unset an environment variable while running this command. */
191 void pipecmd_unsetenv (pipecmd *cmd, const char *name);
192
193 /* Clear the environment while running this command. (Note that environment
194 * operations work in sequence; pipecmd_clearenv followed by pipecmd_setenv
195 * causes the command to have just a single environment variable set.)
196 * Beware that this may cause unexpected failures, for example if some of
197 * the contents of the environment are necessary to execute programs at all
198 * (say, PATH).
199 */
200 void pipecmd_clearenv (pipecmd *cmd);
201
202 /* Install a pre-exec handler. This will be run immediately before
203 * executing the command's payload (process or function). Pass NULL to
204 * clear any existing pre-exec handler. The data argument is passed as the
205 * function's only argument, and will be freed before returning using
206 * free_func (if non-NULL).
207 *
208 * This is similar to pipeline_install_post_fork, except that is specific to
209 * a single command rather than installing a global handler, and it runs
210 * slightly later (immediately before exec rather than immediately after
211 * fork).
212 */
213 void pipecmd_pre_exec (pipecmd *cmd, pipecmd_function_type *func,
214 pipecmd_function_free_type *free_func, void *data);
215
216 /* Add a command to a sequence. */
217 void pipecmd_sequence_command (pipecmd *cmd, pipecmd *child);
218
219 /* Dump a string representation of a command to stream. */
220 void pipecmd_dump (pipecmd *cmd, FILE *stream);
221
222 /* Return a string representation of a command. The caller should free the
223 * result.
224 */
225 char *pipecmd_tostring (pipecmd *cmd);
226
227 /* Execute a single command, replacing the current process. Never returns,
228 * instead exiting non-zero on failure.
229 */
230 void pipecmd_exec (pipecmd *cmd) PIPELINE_ATTR_NORETURN;
231
232 /* Destroy a command. Safely does nothing on NULL. */
233 void pipecmd_free (pipecmd *cmd);
234
235 /* ---------------------------------------------------------------------- */
236
237 /* Functions to build pipelines. */
238
239 /* Construct a new pipeline. */
240 pipeline *pipeline_new (void);
241
242 /* Convenience constructors wrapping pipeline_new() and pipeline_command().
243 * Terminate commands with NULL.
244 */
245 pipeline *pipeline_new_commandv (pipecmd *cmd1, va_list cmdv);
246 pipeline *pipeline_new_commands (pipecmd *cmd1, ...) PIPELINE_ATTR_SENTINEL;
247
248 /* Construct a new pipeline and add a single command to it. */
249 pipeline *pipeline_new_command_argv (const char *name, va_list argv);
250 pipeline *pipeline_new_command_args (const char *name,
251 ...) PIPELINE_ATTR_SENTINEL;
252
253 /* Joins two pipelines, neither of which are allowed to be started. Discards
254 * want_out, want_outfile, and outfd from p1, and want_in, want_infile, and
255 * infd from p2.
256 */
257 pipeline *pipeline_join (pipeline *p1, pipeline *p2);
258
259 /* Connect the input of one or more sink pipelines to the output of a source
260 * pipeline. The source pipeline may be started, but in that case want_out
261 * must be negative; otherwise, discards want_out from source. In any event,
262 * discards want_in from all sinks, none of which are allowed to be started.
263 * Terminate arguments with NULL.
264 *
265 * This is an application-level connection; data may be intercepted between
266 * the pipelines by the program before calling pipeline_pump(), which sets
267 * data flowing from the source to the sinks. It is primarily useful when
268 * more than one sink pipeline is involved, in which case the pipelines
269 * cannot simply be concatenated into one.
270 */
271 void pipeline_connect (pipeline *source, pipeline *sink,
272 ...) PIPELINE_ATTR_SENTINEL;
273
274 /* Add a command to a pipeline. */
275 void pipeline_command (pipeline *p, pipecmd *cmd);
276
277 /* Construct a new command and add it to a pipeline in one go. */
278 void pipeline_command_argv (pipeline *p, const char *name, va_list argv);
279 void pipeline_command_args (pipeline *p, const char *name,
280 ...) PIPELINE_ATTR_SENTINEL;
281
282 /* Construct a new command from a shell-quoted string and add it to a
283 * pipeline in one go. See the comment against pipecmd_new_argstr() above if
284 * you're tempted to use this function.
285 */
286 void pipeline_command_argstr (pipeline *p, const char *argstr);
287
288 /* Convenience functions wrapping pipeline_command().
289 * Terminate commands with NULL.
290 */
291 void pipeline_commandv (pipeline *p, va_list cmdv);
292 void pipeline_commands (pipeline *p, ...) PIPELINE_ATTR_SENTINEL;
293
294 /* Return the number of commands in this pipeline. */
295 int pipeline_get_ncommands (pipeline *p);
296
297 /* Return command number n from this pipeline, counting from zero, or NULL
298 * if n is out of range.
299 */
300 pipecmd *pipeline_get_command (pipeline *p, int n);
301
302 /* Set command number n in this pipeline, counting from zero, to cmd, and
303 * return the previous command in that position. Do nothing and return NULL
304 * if n is out of range.
305 */
306 pipecmd *pipeline_set_command (pipeline *p, int n, pipecmd *cmd);
307
308 /* Return the process ID of command number n from this pipeline, counting
309 * from zero. The pipeline must be started. Return -1 if n is out of range
310 * or if the command has already exited and been reaped.
311 */
312 pid_t pipeline_get_pid (pipeline *p, int n);
313
314 /* Set file descriptors to use as the input and output of the whole
315 * pipeline. If non-negative, fd is used directly as a file descriptor. If
316 * negative, pipeline_start will create pipes and store the input writing
317 * half and the output reading half in the pipeline's infd or outfd field as
318 * appropriate. The default is to leave input and output as stdin and
319 * stdout unless pipeline_want_infile or pipeline_want_outfile respectively
320 * has been called.
321 *
322 * Calling these functions supersedes any previous call to
323 * pipeline_want_infile or pipeline_want_outfile respectively.
324 */
325 void pipeline_want_in (pipeline *p, int fd);
326 void pipeline_want_out (pipeline *p, int fd);
327
328 /* Set file names to open and use as the input and output of the whole
329 * pipeline. This may be more convenient than supplying file descriptors,
330 * and guarantees that the files are opened with the same privileges under
331 * which the pipeline is run.
332 *
333 * Calling these functions (even with NULL, which returns to the default of
334 * leaving input and output as stdin and stdout) supersedes any previous
335 * call to pipeline_want_in or pipeline_want_outfile respectively.
336 *
337 * The given files will be opened when the pipeline is started. If an
338 * output file does not already exist, it is created (with mode 0666
339 * modified in the usual way by umask); if it does exist, then it is
340 * truncated.
341 */
342 void pipeline_want_infile (pipeline *p, const char *file);
343 void pipeline_want_outfile (pipeline *p, const char *file);
344
345 /* If ignore_signals is non-zero (which is the default), ignore SIGINT and
346 * SIGQUIT while the pipeline is running, like system(). Otherwise, leave
347 * their dispositions unchanged.
348 */
349 void pipeline_ignore_signals (pipeline *p, int ignore_signals);
350
351 /* Get streams corresponding to infd and outfd respectively. The pipeline
352 * must be started.
353 */
354 FILE *pipeline_get_infile (pipeline *p);
355 FILE *pipeline_get_outfile (pipeline *p);
356
357 /* Dump a string representation of p to stream. */
358 void pipeline_dump (pipeline *p, FILE *stream);
359
360 /* Return a string representation of p. The caller should free the result. */
361 char *pipeline_tostring (pipeline *p);
362
363 /* Destroy a pipeline and all its commands. Safely does nothing on NULL.
364 * May wait for the pipeline to complete if it has not already done so.
365 */
366 void pipeline_free (pipeline *p);
367
368 /* ---------------------------------------------------------------------- */
369
370 /* Functions to run pipelines and handle signals. */
371
372 typedef void pipeline_post_fork_fn (void);
373
374 /* Install a post-fork handler. This will be run in any child process
375 * immediately after it is forked. For instance, this may be used for
376 * cleaning up application-specific signal handlers. Pass NULL to clear any
377 * existing post-fork handler.
378 *
379 * See pipecmd_pre_exec for a similar facility limited to a single command
380 * rather than global to the calling process.
381 */
382 void pipeline_install_post_fork (pipeline_post_fork_fn *fn);
383
384 /* Start the processes in a pipeline. Installs this library's SIGCHLD
385 * handler if not already installed. Calls error(FATAL) on error.
386 *
387 * The standard file descriptors (0, 1, and 2) must be open before calling
388 * this function.
389 */
390 void pipeline_start (pipeline *p);
391
392 /* Wait for a pipeline to complete. Set *statuses to a newly-allocated
393 * array of wait statuses, as returned by waitpid, and *n_statuses to the
394 * length of that array. The return value is similar to the exit status
395 * that a shell would return, with some modifications. If the last command
396 * exits with a signal (other than SIGPIPE, which is considered equivalent
397 * to exiting zero), then the return value is 128 plus the signal number; if
398 * the last command exits normally but non-zero, then the return value is
399 * its exit status; if any other command exits non-zero, then the return
400 * value is 127; otherwise, the return value is 0. This means that the
401 * return value is only 0 if all commands in the pipeline exit successfully.
402 */
403 int pipeline_wait_all (pipeline *p, int **statuses, int *n_statuses);
404
405 /* Wait for a pipeline to complete and return its combined exit status,
406 * calculated as for pipeline_wait_all().
407 */
408 int pipeline_wait (pipeline *p);
409
410 /* Start a pipeline, wait for it to complete, and free it, all in one go. */
411 int pipeline_run (pipeline *p);
412
413 /* Pump data among one or more pipelines connected using pipeline_connect()
414 * until all source pipelines have reached end-of-file and all data has been
415 * written to all sinks (or failed). All relevant pipelines must be
416 * supplied: that is, no pipeline that has been connected to a source
417 * pipeline may be supplied unless that source pipeline is also supplied.
418 * Automatically starts all pipelines if they are not already started, but
419 * does not wait for them. Terminate arguments with NULL.
420 */
421 void pipeline_pump (pipeline *p, ...) PIPELINE_ATTR_SENTINEL;
422
423 /* ---------------------------------------------------------------------- */
424
425 /* Functions to read output from pipelines. */
426
427 /* Read len bytes of data from the pipeline, returning the data block. len
428 * is updated with the number of bytes read.
429 */
430 const char *pipeline_read (pipeline *p, size_t *len);
431
432 /* Look ahead in the pipeline's output for len bytes of data, returning the
433 * data block. len is updated with the number of bytes read. The starting
434 * position of the next read or peek is not affected by this call.
435 */
436 const char *pipeline_peek (pipeline *p, size_t *len);
437
438 /* Return the number of bytes of data that can be read using pipeline_read
439 * or pipeline_peek solely from the peek cache, without having to read from
440 * the pipeline itself (and thus potentially block).
441 */
442 size_t pipeline_peek_size (pipeline *p);
443
444 /* Skip over and discard len bytes of data from the peek cache. Asserts that
445 * enough data is available to skip, so you may want to check using
446 * pipeline_peek_size first.
447 */
448 void pipeline_peek_skip (pipeline *p, size_t len);
449
450 /* Read a line of data from the pipeline, returning it. */
451 const char *pipeline_readline (pipeline *p);
452
453 /* Look ahead in the pipeline's output for a line of data, returning it. The
454 * starting position of the next read or peek is not affected by this call.
455 */
456 const char *pipeline_peekline (pipeline *p);
457
458 #ifdef __cplusplus
459 }
460 #endif
461
462 #endif /* PIPELINE_H */
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